Effective flight management is closely related to providing accurate and timely information to the pilot. This should be done in a manner that succinctly but accurately conveys to the pilot information important to the safe operation of the aircraft. United States Patents or Patent Applications U.S. Pat. Nos. 5,359,890, 5,412,383, 6,118,385, 6,178,379 and U.S.-2003004619 describe various primary avionics systems including flight display systems and related apparatus. A principal flight instrumentation display is the Primary Flight Display (PFD) on which is shown information about course, speed, altitude, rate of climb and other information. The PFD is usually an electronic display such as a cathode ray tube or back-lit liquid crystal display. FIG. 1 is a simplified schematic example of prior art PFD 10 with electronically driven screen 12. PFD 10 and screen 12 present a variety of flight information. The content of each portion of the display is constrained, that is, specific areas of the display should be used for specific information. This is to simplify pilot training, enhance operational safety and provide for a degree of commonality among the displays in different aircraft.
For example: attitude indicator (AI) 14 located in the upper center shows turn and bank, nose-up, nose down; compass rose (CR) 16 located in the lower center provides course information; course deviation indicator (CDI) or expanded localizer indicator (ELI) 18 located between AI 14 and CR 16 shows lateral deviation from a planned course and Vertical Deviation Indicator VDI 20 located to the immediate right of AI 14 shows vertical deviation from the planned vertical path. CDI 18 has deviation marks (circles) 15 and position indicator (triangle) 17 that moves (as shown by arrows 19) relative to deviation marks 15 in response to deviations from a preplanned or required lateral flight path. Similarly, VDI 20 has elevation marks (circles) 21 and altitude position indicator 23 that moves (as shown by arrows 25) relative to elevation marks 21 in response to deviations from a preplanned or required vertical flight path profile. The spacing of the circular marks in CDI displays 18, 20 represent an angular deviation relative to a beam center of a localizer. The amount of actual course deviation needed to produce one marker displacement of position indicators 17, 23 in the directions of arrows 19, 25 is determined by minimum sensitivity requirements specified as a range or minimum by certification or industry standards scale of the indicator. A variety of other information is also presented on PFD 10 located around these required displays. For example, airspeed is generally shown in location 20, angle of attack in location 22, altitude in location 24 and vertical speed in location 26. Various other information is presented in locations 28-56, as for example, legends such as FMS1 (flight management system—one), ADF1 (automatic direction finder—one), VOR2 (omni-range beacon—two), etc. These legends may be turned on or off as the flight progresses.
One of the limitations of prior art PFDs is that they do not provide sufficient navigation information to the pilot when the plane is in highly restricted airspace or if they provide such information it is not presented in an easily comprehended way that relates to most pilot's previous experience. Restricted airspace often occurs under Category I and Category II instrument landing system (ILS) approach conditions. Category II is more restricted than Category I. What is needed, among other things, is presentation of the Required Navigation Performance (RNP) data associated with such restricted airspace, compared to the Estimated Position Uncertainty (EPU) of the aircraft. RNP is defined as [see ICAO Doc. 9613]: A statement of the navigation performance accuracy necessary for operation within a defined airspace. EPU is defined as [see RTCA SC-181/EUROCAE WG-13]: A measure based on a defined scale in nautical miles or kilometers which conveys the current position estimation performance.
Because of the already crowded and busy nature of the PFD screen, it is difficult to add new information in a manner that can be easily and quickly grasped by the pilot. In general, the new information almost always has to be placed in an already defined field on the display. However, it cannot replace unrelated essential information. For example, more detailed navigation information cannot be placed in the display area reserved for a different category of information such as speed, altitude, heading, etc.
U.S. patent application US-2003004619 describes a display system adapted for use on a PFD that shows CDI indications (both lateral and vertical) that combine RNP and Actual Navigation Performance (ANP) information. The system described therein uses extensible bars whose outer ends correspond to the RNP limit and whose inner ends are determined by the ANP value relative to the RNP value. The center marker between the bars corresponds to the planned aircraft course. A separate pilot controlled “bug” indicates the current aircraft position relative to the next course. If the current position indicator lies in the space between the extensible bars, the aircraft is operating in a safe region, and if the current position indicator lies on either of the extensible bars, the aircraft is no longer in a safe operating region. While this approach provides more information for operation in an RNP region than, say, the display of FIG. 1 it is less than optimal. Among its limitations are: (i) combining the RNP and ANP information into the extensible bars makes it difficult or impossible for the pilot to estimate whether the potential navigation problem arises from RNP or ANP variations or both since they are not separately presented; (ii) the mode of presentation using the extensible bars is, for some people, more difficult to relate to the spatial geometry of the flight path and the aircraft position; (iii) there are no scale reference markers on the CDI display using the extensible bars so that relative separation of safe and hazardous operating conditions may be harder for some pilots to judge; and (iv) the current position indicator is not correlated on the display with the ANP information.
Accordingly, it is desirable to provide more detailed navigation information for safe operation in restricted airspace, in a manner that is more intuitive and more easily grasped by a pilot, that conveys more clearly a geometric picture related to the actual flight path and navigational limitations. In addition, it is desirable to provide such information in a way that does not interfere with unrelated information already present on the PFD screen. Further, it is desirable to provide such additional navigation information so that it is within the pilot's primary PFD scan area at all times. Still further, it is desirable that the additional information be provided in such a way that the improved display can be retrofitted to existing fleets with minimum system alterations. In addition, other desirable features and characteristics of the present invention will become apparent from the subsequent detailed description of the invention and the appended claims, taken in conjunction with the accompanying drawings and this background of the invention.